Editorials
Digestive system diseases
Volume 214 - Issue 8

The increasing burden of inflammatory bowel disease

Author:  Edward V Loftus

Med J Aust 2021; 214 (8): 361-362. || doi: 10.5694/mja2.51001
Published online: 3 May 2021
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Until we reach “prevalence equilibrium”, even small increases in incidence eventually result in higher prevalence

When I attended medical school in the 1980s, we were taught that ulcerative colitis and Crohn disease were conditions seen in white people in highly developed regions such as northern Europe, the United Kingdom and some Commonwealth nations, and North America. Over the past four decades, the incidence of inflammatory bowel disease (IBD) across geographic regions and ethnic groups has risen sharply.1 The global burden of IBD, which can substantially reduce quality of life, is clearly increasing.2 Patients with IBD often require expensive medications or procedures,3 have higher rates of anxiety and depression,4 and are more likely to have disabilities.5

The prevalence of a chronic disease (number of new and old cases per number of persons) roughly corresponds to the incidence (number of new cases per person‐years) multiplied by the mean duration of the condition.6 For IBD, for which the median age at diagnosis is 30–35 years7 and life expectancy is normal or near normal,8 the prevalence will ultimately be 30 to 50 times the incidence rate. Consequently, even small increases in incidence will eventually result in higher prevalence, especially when the incidence rate is higher than the mortality rate. This concept of “compounding prevalence” has only recently been applied to IBD,9 but it is an extremely accurate description.

We are now seeing these effects in several areas of the world. In Canada, the prevalence of IBD may be as high as 700 cases per 100 000 population;10 the prevalence may be even higher in the Lothian region of Scotland, where it is estimated to exceed 800 cases per 100 000 population and is projected to rise over the next eight years to more than 1200 per 100 000.11 To put this into context, the global age‐standardised prevalence of IBD in 2017 was estimated to be 84.3 cases per 100 000 population.2

The high prevalence of IBD in the City of Canada Bay in metropolitan Sydney described in this issue of the MJA by Pudipeddi and colleagues12 fits this pattern. The reported overall age‐standardised prevalence of about 350 cases per 100 000 population means that 1 in 280 people in this region has ulcerative colitis or Crohn disease, and prevalence rises with age, to roughly 1 in 160 people aged 65 years or more. On the basis of their findings, the authors estimate that more than 81 000 Australians have IBD.

Most patients with IBD are diagnosed before the age of 40 years. Higher prevalence in older people may be partly explained by the inverse epidemiological association between cigarette smoking and ulcerative colitis, one of the few conditions against which cigarette smoking is seemingly protective;13 most patients with ulcerative colitis are never or former smokers. In Olmsted County, Minnesota, for example, mortality among patients with ulcerative colitis is actually lower than for the general population, as any increase in deaths related to gastrointestinal causes or cancers is more than offset by lower cardiovascular mortality.8 This consideration would, however, not apply to Crohn disease.

We must also remember that the typical patient with IBD is diagnosed in their 20s or 30s, but more than one‐third of people with Crohn disease and 40% of those with ulcerative colitis are diagnosed after the age of 40 years.7 In fact, the age at diagnosis in Olmsted County and some other regions has a bimodal distribution, with a second peak in incidence later in life,8 although some diagnostic confusion — older people with diverticulitis or ischaemic colitis being diagnosed with IBD — is possible.14 Another explanation for increasing prevalence with age in the study by Pudipeddi and colleagues may be the ethnic makeup of suburban Sydney, in which more than 15% of residents are Asian.12 Studies in Asian countries have reported higher median ages at IBD diagnosis.15,16

Why is the higher prevalence of IBD among older people important? Although some studies have suggested a milder disease course for those diagnosed with IBD later in life,17 they comprise only a minority of older people with IBD; in the Canada Bay study, only 25% of patients with IBD had been diagnosed after the age of 48 years.12 Older patients with IBD can be more difficult to manage, as they are two to three times as likely to have serious infections after treatment with biologics,18 and post‐operative morbidity and mortality are significantly more likely than for younger or middle‐aged adults.19 Older patients are also more likely to meet the definition of “frailty”, itself associated with higher rates of serious adverse events during immunosuppressive therapy,20 and mortality and re‐admission rates for hospitalised patients with IBD are higher.21 I agree with the recommendation by Pudipeddi and his colleagues to consider non‐systemic immunosuppressive therapies when possible.

Until we reach “prevalence equilibrium”22 — that is, when prevalence stabilises because the overall mortality rate is equal to the incidence rate — physicians and health authorities need to continue adjusting to the increasing burden of IBD.

 

Author

  • Edward V Loftus1
  • 1. Mayo Clinic, Rochester, MN, United States of America

Correspondence: loftus.edward@mayo.edu

Competing interests

I have provided consultation services to AbbVie, Amgen, Allergan, Boehringer Ingelheim, Bristol‐Myers Squibb, Celgene, Celltrion Healthcare, Eli Lilly, Genentech, Gilead, Iterative Scopes, Janssen, Ono Pharma, Pfizer, Takeda, and UCB. I have received research support from AbbVie, Amgen, Bristol‐Myers Squibb, Celgene, Genentech, Gilead, Janssen, Pfizer, Receptos, Robarts Clinical Trials, Takeda, and UCB. I am a shareholder in Exact Sciences.

References

Linked content

  • MJA Research: High prevalence of Crohn disease and ulcerative colitis among older people in Sydney

Provenance: Commissioned; externally peer reviewed.

View this article on Wiley Online Library